From Wikipedia, the free encyclopedia

A spectrum (plural spectra or
spectrums[1]) is a
condition that is not limited to a specific set of values but can
vary infinitely within a continuum. The word saw its first
scientific use within the field of optics to describe the rainbow of colors in visible light when
separated using a prism; it
has since been applied by analogy to many fields other than optics.
Thus, one might talk about the spectrum of political
opinion, or the spectrum of activity of a drug,
or the autism spectrum. In these uses,
values within a spectrum may not be associated with precisely
quantifiable numbers or definitions. Such uses imply a broad range
of conditions or behaviors grouped together and studied under a
single title for ease of discussion.

In most modern usages of spectrum there is a unifying
theme between extremes at either end. Some older usages of the word
did not have a unifying theme, but they led to modern ones through
a sequence of events set out below. Modern usages in mathematics
did evolve from a unifying theme, but this may be difficult to
recognize.

The term spectrum was soon applied to other waves, such as
sound
waves, and now applies to any signal that can be decomposed
into frequency components. A spectrum is a usually 2-dimensional plot, of a
compound signal, depicting the components by another measure.
Sometimes, the word spectrum refers to the compound signal
itself, such as the "spectrum of visible light", a
reference to those electromagneticwaves which are visible to the humaneye. Looking
at light through a prism separates visible light into its colors
according to wavelength. It separates them according to its
dispersion relation and a grating separates according to the
grating equation and if massive particles are measured often their
speed is measured. To get a spectrum, the measured function has to
be transformed in their independent variable to frequencies and the
dependent variable has to be reduced in regions, where the
independent variable is stretched. For this imagine that the
spectrum of pulse with a finite number of particles is measured on
a film or a CCD. Assuming no particles are
lost, any nonlinearity (compared to frequency) on the spectral
separation concentrates particles at some points of the film. The
same is true for taking a spectrum by scanning a monochromator with
a fixed slit width. Violet at one end has the shortest wavelength
and red at the other end has the longest wavelength of visible
light. The colors in order are violet, blue, green, yellow, orange,
red. As the wavelengths get bigger below the red visible light they
become infrared, microwave, and radio. As the wavelengths get
smaller above violet light, they become ultra-violet, x-ray, and
gamma ray.

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details as well as a {{system}} infobox. Reliable information can
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The Sinclair ZX Spectrum was a home computer
released in the United Kingdom by Sinclair Research in 1982. While
originally called the "ZX82", the system was renamed the ZX
Spectrum in order to promote its colour display. It proved
immensely popular in various incarnations over the years and
remains the most successful British computer ever made.

A spectrum (plural: spectra or spectrums[1]) is a band of several colours, violet, indigo, blue, green, yellow, orange and red. A spectrum can be seen if the Sun's light is passed through a prism and allowed to gather on a white screen.[2] A natural example of a spectrum is a rainbow. The word spectrum was first used by scientists studying optics. They used the word to describe the rainbow of colors in visible light when separated using a prism. The spectrum seen when light passes through a prism is an example of the dispersion of light. The material from which the prism is made has a different refractive index n than air. Usually, nprism is greater than nair, and nair is taken to be approximately one. This implies that light travels a little slower in the material of the prism than in the space surrounding it. The angle of refraction can be determined from the angle of incidence and the refractive indexes using Snell's law. The reason why the white light separates into in its component colors instead of remaining white is because the shorter wavelengths are refracted, or bent, more than the longer wavelengths. Thus, red, having the longest visible wavelength, will appear closest to the line perpendicular to the surface of the material (the normal), that is, it will be bent the least. Violet light, with the smallest wavelength in the visible spectrum, will be bent the most. The rainbow produced will always be in the same order: red, orange, yellow, green, blue, indigo, violet.